1. Field of the Invention
This invention relates to biopsy needles and, more particularly, to an improved fine needle aspiration biopsy needle apparatus and method for improved cell harvesting.
2. The Prior Art
Cytologic analysis is being increasingly utilized for the early detection of cancer or other abnormalities in the cellular structure of an organ such as a breast. The early detection of such cancers can be especially important. Studies have shown that cytologic analysis will reveal the presence of a precursor lesion, atypical ductal hyperplasia, several months before microcalcifications are detected during a standard mammography procedure. In one case, fine-needle aspirates revealed atypical ductal hyperplasia in three quadrants of the right breast one year before microcalcifications in that breast were detected by mammography. A second set of fine-needle aspirate samples was obtained at the time of the abnormal mammography; these revealed malignant cells in the same quadrant in which the abnormality was identified, as well as atypical hyperplasia in both the right and left breast. Subsequent biopsy revealed intraductal carcinoma, confirmed by histology. In the second case, the initial fine-needle aspirates showed atypical ductal hyperplasia in one breast concurrent with a suggestion of breast cancer in that breast on mammography. Breast cancer was subsequently confirmed by histology.
It has been hypothesized that in hereditary cancer, the initial alternation, or susceptibility to it, is inherited as a dominant gene, and that further mutational events cause lesion appearance and progression to malignancy. The analysis of the adenomatous polyp as the precursor for colon cancer is the most refined demonstration of a cancer precursor. Adenomatous polyps are known to be inherited, and deletions of tumor suppressors and activation of oncogenes in adenomatous polyps have been demonstrated in their conversion to malignancy. It is postulated that this process is analogous to the development of proliferative breast disease (PBD) and its conversion to breast cancer, except that PBD appears to be a more diffuse lesion. A recent study discusses PBD as an inherited disease and is reported in a scientific journal wherein I am one of the authors, Science Vol. 250, 21 Dec. 1990, pages 1715-1720, "Inheritance of Proliferative Breast Disease in Breast Cancer Kindreds."
From the foregoing it is clear that cytologic analysis of fine-needle aspirates is only as good as the aspirate obtained. Currently, aspirates are obtained from a breast, for example, using a 2.5 cm, 22-gauge needle mounted on a syringe. The syringe is used to apply a negative pressure of about 15 ml. The needle can also be attached to a syringe pistol for convenience in attaining the necessary negative pressure. Historically, the needle has been a conventional needle with a sharpened tip. The aspirate is obtained by the combination of the negative pressure and the cutting action of the sharpened tip. However, I have determined that the aspirate obtained by this standard technique is not consistently accurate in obtaining representative samples from the tissue into which the needle is inserted. This problem is extremely serious particularly in light of the high degree of reliance being placed on cytologic analysis as a cancer screening technique.
It is estimated that the false negative rate for the current state of the art biopsy needle is at least 15. The primary reason for this dangerously high false negative rate is directly related to the present design of the biopsy needle. In particular, aspirate from tissue obtained by conventional fine-needle aspiration biopsy techniques relies solely upon the cutting action of the sharpened end of the needle in combination with suction from inside the needle. Experience has shown that for some as yet unexplained reason, the aspirate obtained by this technique falls short of accurately representing the full range of cellular material through which the needle has passed. One possible explanation is that the cutting action of the needle dislodges a relatively large piece of noncritical tissue which temporarily blocks the needle from receiving additional aspirate from the surrounding tissue. This, in turn, means that the needle is not collecting aspirate during this portion of its traverse through the tissue.
Another possible theory is that the sharpened needle acts as a "corer" in that it cuts a core of tissue, the core having a length incrementally less than the distance of penetration of the needle in the tissue. Such a core is almost never obtained along the entire depth of penetration by the needle. Further, such a sample, if it were obtainable on a consistent basis would be too large an aspirate for accurate cytological examination. In any event, pathologists prefer free cells rather than tissue cores to conduct a proper cytological examination.
Needle cannulae are known in the art and are used for a number of medical applications including, for example, Anesthesiology, Angiography, Myelography, Roentgenography, and Ventriculography. As cannulae, these needles are specifically designed with relatively large single, double, or even triple holes, all of which are spaced from the pointed tip which is generally a closed point. If one were to attempt to use one of these needle cannulae as a biopsy needle there is a high probability that the relatively large holes in the sidewall would allow the suction inside the needle to pull the surrounding tissue into the lumen of the needle thereby temporarily plugging the needle against the further collection of aspirate.
Another disadvantage of the attempted adaptation of the prior art needle cannulae as a biopsy needle is absence of an aspirate collection reservoir in the hub as well as the lack of outwardly extending wings on the hub to assist in the safe, convenient handling of the needle. Further, since the needle cannulae are designed as cannulae, as the name implies, they do not include an indicia to indicate the withdrawal limit for the needle.
It would, therefore, be a significant advancement in the art to provide an improved needle apparatus and method for obtaining aspirates using fine-needle biopsy techniques. It would also be an advancement in the art to provide an improved biopsy needle for obtaining a more comprehensive aspirate from the tissue through which the needle is passed. Another advancement in the art would be to provide a biopsy needle that is easier to use and safer to handle. An even further advancement in the art would be to provide the biopsy needle with a marker to alert the physician when the needle has been withdrawn to the maximum withdrawal length prior to reinsertion at a different angle so as to preclude aspiration of air upon complete withdrawal of the biopsy needle from the tissue. Such a novel apparatus and method is disclosed and claimed herein.